This invention is related to control systems, and, more particularly, to morning start-up control systems for controlling the temperature control system of a building.
Many buildings, such as office buildings, schools, factories and the like are only occupied during certain hours of the day, certain days of the week. During these "occupied" hours, it is desirable that the internal temperature of these buildings be maintained at some predetermined comfortable level. On the other hand, it is inefficient from an energy conservation point of view for the temperature of such buildings to be maintained at a comfortable level during the hours that they are unoccupied. For this reason, the internal temperatures of such buildings are allowed to fluctuate from a comfortable level during unoccupied periods by resetting the building's thermostat or by turning the building's heating and/or cooling system off. In cooler climates the "night" setting allows the building's temperature to drop and in warmer climates it allows the building's temperature to rise. Because the building temperature is allowed to fluctuate during unoccupied periods, it is necessary to bring the building's temperature back to a comfortable level by the time occupancy is to commence. Obviously, a time delay is involved in this process because a building's temperature cannot be raised or lowered instantaneously.
In the past, fixed period timers have been used to switch a building's heating and/or cooling system from a night setting to a "day" setting some fixed period of time prior to occupancy. In this manner the building temperature is brought to a comfortable level prior to occupancy. The period of time between switching from the night setting until the day comfort temperature level is reached is commonly referred to as the morning start-up period.
There are, obviously, a number of disadvantages to a fixed morning start-up period. For example, if the morning start-up period begins too early, energy is wasted because the building is brought to the desired temperature level well prior to occupancy. Alternatively, if the morning start-up period begins too late, the occupants will be uncomfortable because the building will not be at the desired temperature level when occupancy commences.
At this point it should be noted that the desired morning start-up period (desired meaning the minimum time necessary to bring the building's temperature to a desired level at the precise time occupancy commences) is not a fixed period of time. Rather, it varies from day-to-day, depending on external temperature and wind conditions, and the construction and insulation parameters of a particular building, because all of these elements determine the amount of temperature fluctuation (i.e. heat loss or gain) that will occur during the unoccupied periods and the amount of time it will take for the building's temperature to be brought to a comfortable level from any other level.
In the past, temperature sensors have been used to control the morning start-up period on a day-to-day basis. One such prior art system is described in U.S. Pat. No. 3,317,692 issued May 2, 1967 to James L. Duncan, for Ambient Temperature-Modified, Temperature-Altering Control Mechanism. While systems of the nature described in this patent are a step forward from fixed morning start-up period systems, they still have a number of disadvantages. For example, these systems are basically mechanical in nature. Thus, they are subject to mechanical failures. Further, these systems use temperature sensitive devices that are relatively imprecise. More specifically, these systems preferably use temperature sensitve devices whose position or tension is related to temperature. Because these devices are constantly tensed, they rapidly deteriorate with age. As they deteriorate, their temperature/mechanical force relationship varies from a nominal value. Finally, mechanical systems of this nature are difficult to precisely adjust to compensate for different building parameters. In fact, most such systems cannot be adjusted to compensate for such parameters.
Therefore, it is an object of this invention to provide a new and improved building temperature control system.
It is a further object of this invention to provide a variable morning start-up period control suitable for use in controlling the heating and/or cooling system of a building that is reliable and long lasting.
It is a still further object of this invention to provide a new and improved morning start-up building temperature control that is formed mainly of electronic components and, therefore, easily adjusted and reliable.